1. Field of the Invention
This invention relates to surge voltage arrestors with graphite ignition lines therein, and more particularly to an apparatus for applying the ignition lines.
2. Prior Art
In the construction and operation of open ar transmission lines and cables, particularly in association with communication installations, provision must be made to deal with external surge voltages. Additionally, internal surge voltages can also arise, for example as a result of intentional or unintentional switching operations occurring in installations and devices associated with the apparatus. In order to avoid damages which can result from such surges, and in order to further minimize the danger to individuals working around such equipment it is necessary to provide means to limit the surge voltages to harmless values. For this purpose, it has been known to use surge voltage arrestors having electrodes located in an inert gas atmosphere. Such voltage arrestors generally consist of hollow cylindrical glass members filled with inert gas, the glass cylinders having an opposed axial ends sealed gas tight by caps which form spaced apart electrodes. In order to provide for stable ignitions at preselected minimum threshold voltages, devices identified as ignition lines are provided in the hollow cylindrical glass members.
The ignition lines which function in the manner of an internal electrode, are formed by means of elongated relatively narrowed dashlike electrically conductive coatings on the interior wall of the glass member. The length of the ignition line is maintained less than the glass member so that predetermined clearance distances are maintained between the ignition line, or lines and the respective end electrodes.
The insertion of the ignition line into the hollow cylindrical glass member has, heretofore, been carried out manually by the application of a suspension of colloid graphite in water, the application being by means of brush. Such prior techniques have not been automatable and quality control is difficult. One identifiable problem is the fact that the solid ingredients of the graphite suspension settle out of the suspension and thus the amount of colloid graphite which will deposit at any given time by the brush technique is not predeterminable.
It would therefore be an improvement in the art of manufacture of surge voltages arrestors to provide an apparatus for the insertion of ignition lines in the hollow cylindrical glass members of such arrestors which method is easily automatable and which will provide for the application of a sufficiently precise predetermined amount of electrically conductive coating by the automated equipment.